Fabric forms, and fabrics for making the same have been receiving a considerable amount of attention from innovators, as evidenced for example, by the issuance of U.S. Pat. Nos. 3,486,341; 3,524,320; 3,570,254; 3,517,707; and 3,837,169.
Most of the inventive effort as reflected in these patents, has been directed to the provision of restraining means to limit and control the thickness of the forms as they are filled with concrete. There are at least three reasons why controlled thickness is important. First, it conserves filler material. Second, it produces an aesthetically pleasing surface configuration. Third, in some instances, it allows a measure of predictable control of cracking of the concrete monolith within the form, in cases where heaving and settling create forces which exceed the elastic limit of the concrete structure. This controlled cracking is desirable since it permits the concrete structure to conform itself to changing profiles in the underlying, river bank, channel floor, coast line or the like.
In some of the earlier efforts, as evidenced by U.S. Pat. Nos. 3,486,341; 3,524,320; and 3,570,254, uniformly spaced wire ties were employed to limit the thickness of the fabric form.
In U.S. Pat. No. 3,517,707 "drop stitches" were woven into a dual layer fabric, to extend from one layer of fabric to the other, and thereby limit the distance by which the two layers of fabric could be separated.
U.S. Pat. No. 3,837,169 employs cord systems disposed internally of the fabric form to limit its cross-section and configuration.
While each of the systems employed by the prior art is useful, no one is without its drawbacks. Thus, for example, the network of wires disclosed by U.S. Pat. No. 3,524,320 is tedious to install and expensive from the standpoint of the amount of hand labor involved.
The "drop stitch" arrangement disclosed in U.S. Pat. No. 3,670,504 while desirable from a standpoint that virtually no on-site construction is required, suffers the disadvantage that the number of drop stitches required to achieve the thickness control is so great that the crisscrossing fibers tend to impede the flow of concrete within the fabric container, making it difficult to fill the form.
U.S. Pat. No. 3,837,169 by its disclosure constitutes an improvement over the foregoing prior art techniques, and indeed overcomes many of the problems associated with the earlier thickness control systems. The present invention moves one step further in the direction of reducing the amount of hand labor required to install the means for controlling the thickness of the form, while maintaining the interior of the form relatively uncluttered to permit the movement of flowable concrete without significant impediment.